The Sensitivity Interface
The Sensitivity (sens) interface (), found under the Mathematics>Optimization and Sensitivity () branch when adding a physics interface, provides tools for adding advanced sensitivity evaluation to a stationary model. Basic problems defined only in terms of global scalar objective functions and model parameters can be set up directly in a Sensitivity study step and therefore do not require the use of a Sensitivity interface.
For a more extensive introduction to the mathematics implemented by this physics interface, see the Theory for the Sensitivity Interface.
The objective functions are defined in terms of control and solution variables (the latter are given as the solution to the differential equations defined by the multiphysics model), which can be fields dependent on position in space or scalar quantities defined globally. This flexibility is reflected in the physics interface by grouping these settings according to the dimension of the domain to which they apply. In such a group of settings, the following settings can be specified, to which each corresponds a separate feature and its Settings window:
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Integral Objective
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Probe Objective
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Control Variable Field
Note that adding a Sensitivity study step to a study makes it possible to perform a sensitivity analysis directly at the study level. See Sensitivity.
Sensitivity Toolbar
The following nodes are available from the Sensitivity ribbon toolbar (Windows users), Sensitivity context menu (Mac or Linux users), or by right-clicking to access the context menu (all users).
For step-by-step instructions and general documentation descriptions, this is the Sensitivity toolbar.
Table 17-1: The Sensitivity toolbar.
Button or Menu
Name
 Physics
Add Physics
 Global
Global Objective
Global Control Variables
The main Settings window for the Sensitivity node contains the following section:
Settings
The Label is the default physics interface name.
The Name is used primarily as a scope prefix for variables defined by the physics interface. Refer to such physics interface variables in expressions using the pattern <name>.<variable_name>. In order to distinguish between variables belonging to different physics interfaces, the name string must be unique. Only letters, numbers, and underscores (_) are permitted in the Name field. The first character must be a letter.
The default Name (for the first physics interface in the model) is sens.
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Common Physics Interface and Feature Settings and Nodes
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Global Objective
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Global Control Variables
Sensitivity Analysis of a Communication Mast Detail: Application Library path COMSOL_Multiphysics/Structural_Mechanics/mast_diagonal_mounting_sensitivity